Giving language skills a boost

Do temporal processing deficits cause phonological processing problems?

This study tested the hypothesis that temporal processing deficits underlie phonological processing problems. The subjects were children aged 8 to 10 years (N = 110) who were separated into 2 groups on the basis of whether their reading scores were normal or poor. As predicted by many earlier studies, children with poor reading scores demonstrate poor abilities on tests of phonological awareness, as well as on 2 other language tasks that depend on phonological processing. Two specific tests of the temporal processing hypothesis were conducted. Children in both groups were tested (a) on their abilities to recall sequences of nonspeech tones presented at various rates and (b) on their abilities to make phonetic decisions using brief and transitional properties of the speech signal, especially formant transitions (the purported "trouble spot" in the speech signal for children with phonological processing problems). The children with poor phonological processing abilities showed no special difficulty recalling rapidly presented nonspeech stimuli, and, in their phonetic decisions, they were able to use brief and transitional signal properties, including formant transitions, at least as well as other children. Therefore, no evidence was found to support the hypothesis that temporal processing deficits cause phonological processing problems.

Checks and Balances

Kamhi (1999) suggests that clinicians may choose to use an intervention approach "because it works" rather than relying on their theory of language learning. This suggestion spawned a number of concerns, including who the scientists in our field are, whether our professional definition of language is used in our language theories and intervention approaches, and what we say the "best" intervention is. In this article, these issues are discussed as discrepancies, along with some suggestions for addressing these gaps, in order to integrate science into all of our professional endeavors.

Auditory temporal coding in dyslexia

Developmental dyslexia is generally believed to result from impaired linguistic processing rather than from deficits in low-level sensory function. Challenging this view, we studied the perception of non-verbal acoustic stimuli and low-level auditory evoked potentials in dyslexic adults. Compared with matched controls, dyslexics were selectively impaired in tasks (frequency discrimination and binaural unmasking) which rely on decoding neural discharges phase-locked to the fine structure of the stimulus. Furthermore, this ability to use phase-locking was related to reading ability. In addition, the evoked potential reflecting phase-locked discharges was significantly smaller in dyslexics. These results demonstrate a low-level auditory impairment in dyslexia traceable to the brainstem nuclei.